Electronic particle study apparatus with fluid circulating system

ABSTRACT

Electronic particle study apparatus for studying particles, particularly those whose density and size make difficult maintenance of a dispersion in a fluid medium and which permits total sample recovery. A pair of chambers is provided through which a continuously filtered electrolyte flows. The chambers are separated by a Coulter type scanning aperture means and drip chamber means is provided for electrically isolating one of said chambers. A recirculating system for supplying filtered electrolyte to the chambers including storage means, recirculating means, pump means and filter means, for moving of the electrolyte into and out of the chambers and for collecting the particulate sample.

United States Patent Claps 1 Aug. 29, 1972 [54] ELECTRONIC PARTICLE STUDY APPARATUS WITH FLUID Primary Examiner-Rudolph V. Rolinec CIRCULATING SYSTEM Assistant Examiner-David M. Carter [72] Inventor: William A. Claps, Hialeah, Fla. Attmey sllverman & Cass [73] Assignee: Coulter Electronics, Inc., Hialeah, ABSTRACT Electronic paru'cle study apparatus for studying parti- [22] Filed: Sept. 10, 1970 I cles, particularly those whose density and size make difficult maintenance of a dispersion in a fluid medium [21] P" 71,160 and which permits total sample recovery. A pair of chambers is provided through which a continuously 52 US. Cl. ..324/71 CP, 204/195 filtered electrolyte flows- The Chambers are Separated 51 Int. Cl. ..G0la 27/08 by a Cwltef type Scanning alPermre means and drip 581 Field of Search ..324/71 71 CP' 204/195 chamber means is Pmvided elmmally Mating one of said chambers. A recirculating system for sup- [56] References Cited plying filtered electrolyte to the chambers including storage means, recirculating means, pump means and UNITED STATES PATENTS filter means, for moving of the electrolyte into and out 1 3,461,030 8/1969 Keyes ..324/71x chambers and the Pamcula 3,369,984 2/1968 Gerdes et al ..204/ 195 3,395,343 7/1968 Morgan et a1. ..324/71 24 Claims, 6 Drawing figures /44/ /42 mo f: M as, I24 /0 ,f /ze 19a 68 L r! E;

1 \YF l (255 /0@ l -ro""1 mama 1 64 I 6 m9 26 v I /20 /04 if t Z 66 2 /24 $2 62 #16 M I 92 F J /3 //4 A 1 94 i 6 w 1'; L 1 /29 p v 96 V 5 M4 m5 4? p (96/ cf ELECTRONIC PARTICLE STUDY APPARATUS WITH FLUID CIRCULATING SYSTEM FIELD OF THE INVENTION This invention relates generally to electronic particle study apparatus and more particularly provides means whereby particulate samples of size and density incapable of being retained in suspension may be studied utilizing the Coulter principle yet with substantially total sample recovery.

RELATION TO EARLIER PATENTS This invention is an improvement on the electronic particle study apparatus described in U.S. Pat. No. 3,395,343 granted to Morgan et al. and assigned to Coulter Electronics Inc., the assignee of the instant application.

BACKGROUND OF THE INVENTION The Coulter principle of particle study asserts that a particle, suspended in a fluid medium, passing through a microscopic aperture changes an electrical characteristic of the fluid within the aperture by an amount functionally related to the size of the particle. Accordingly, a suspension of particles to be studied is prepared and placed in a first vessel and second vessel having a small aperture in the side wall thereof is immersed into the first vessel to place the aperture within the suspension. Fluid is withdrawn from the second vessel, drawing the suspension from the first vessel through the aperture. Electrodes of non-corrosive metal are suspended in the fluid of both vessels and external leads pass from these respective electrodes to a detecting device, such as the input of a counting means. An electric current is caused to flow between the electrodes through the respective bodies of fluid and through the aperture. Each time the particle is drawn through the aperture there will be detectable change in a measured electrical characteristic of the aperture which will produce an electrical signal transmitted through the detector and amplified so that it can be measured and counted.

The second vessel referred to above has come to be known generally as the Coulter aperture tube and carries the aperture. The typical aperture tube is constructed generally as shown in Coulter et al. U.S. Pat. No. 2,985,839, wherein the Coulter aperture is formed by drilling a minute hole in a thin wafer of vitreous material such as sapphire and cementing or fusing the wafer to a side wall of a tube over a relatively large orifice previously formed in a tube. The aperture is positioned to facilitate flow of this suspension from one vessel to the other through the aperture without adverse statistical effects caused by drawing from a settled portion of the first vessel.

For the purposes of this description reference hereinafter shall be made to a structure termed a Coulter scanning aperture means. In Coulter U.S. Pat. No. 2,656,508, the said scanning aperture comprises an opening of microscopic proportion formed in a wall of a fluid holding vessel through which aperture particles are passed. The aperture may also be provided as in Coulter et al. U.S. Pat. No. 2,98,830, wherein the microscopic dimension aperture is provided in a wafer of generally heat resistant vitreous material and a larger orifice is formed in the wall of the vessel, the orifice being of predetermined contour, and the wafer carrying the microscopic dimension aperture is secured to the vessel wall with the orifice and aperture aligned. This structure shall be hereinafter referred to in this application as Coulter scanning aperture means," which term is used to describe that portion of a wall which carries the aperture, as well as the aperture itself whereat the effects measured actually occur.

In the earlier U.S. Pat. Nos. 2,656,508 and 2,985,830 which describe embodiments presently commercially available under the registered trademark Coulter Counter, manufactured by Coulter Electronics Inc. of Hialeah, Fla., particles capable of being studied are many and varied but all share a common characteristic and that is, all are capable of being suspended in a fluid medium of conductivity different from that of the particles to be measured.

Since the particles in sample suspension are carried through the aperture into the relatively small volume aperture tube of the Coulter apparatus and into the fluid system, the particles counted inside normally are lost and never recovered, being removed from time to time with continued removal of the fluid from the interior of the Coulter aperture tube by, for example, a vacuum source. Many of the particles to be studied re valuable and must be recovered. These include extremely pure metals, gold, radioactive materials such as uranium isotopes, and the like. Many particles are products in a continuing research program and also require recovery for further processing, testing and studying. Thus means for obtaining total recovery of the sample are desirable. Another problem involved, particularly with the use of relatively heavy particles which soon settle out of any suspension, is that the previously available Coulter aperture tubes are immersed in the sample containing vessel with the aperture spaced from the bottom of the sample containing vessel. Thus it was not possible to complete the sizing and counting of all the particles in this sample. Statistical sampling was difficult particularly where heavier particles are concerned since these particles tend to separate from the suspension and, due to gravational forces, collect near the bottom of the sample holding vessel spaced from the vicinity of the aperture. Difficulty occurred in maintaining agitation since the level in the vessel concerned would decrease.

In U.S. Pat. No. 3,395,343, a vessel construction for use with an electronic particle study apparatus of the Coulter type was provided wherein the vessel comprised a pair of beaker like vessels of insulating material arranged nested one within the other and having the rims thereof in sealed relationship to define an enclosed chamber. The inner one of the vessels function as a sample chamber and carried a precise microscopic dimension aperture in the bottom wall thereof. The enclosed vessel functioned as the second vessel of the Coulter apparatus so that the sample was introduced into the inner vessel and drawn through the aperture, into the enclosed second vessel. Means leading to a vacuum source for drawing the sample suspension from the inner vessel to the enclosed chamber were so arranged relative to the aperture means that the heavy particles would be retained within the enclosed chamber to be later recovered as a residium subsequent to such determinations.

One of the problems involved in utilization of the previous vessel construction was that with a decreasing level in the inner vessel, portions of the sample did not pass through the aperture. Necessary agitation scattered many particles about the vessel, as well. l-l nce counting and study in its entirety of a particulate Sarnple not capable of being retained in a suspension was not possible. Further, it is still possible for some of the sample to be lost with the heavier portions being retained.

Accordingly the principal object of this invention is to provide an electronic particle analyzing apparatus for utilization in the study and analysis of relatively heavy particles for total sample recovery.

Another object of this invention is to provide, in an electronic particle analyzing apparatus, means to prevent the sample containing chamber or vessel from being depleted of a fluid by continuouly replacing electrolyte therein with clean filtered electrolyte to avoid the absence of an electrolyte path between the scanning aperture means and measuring electrodes.

Further object of this invention is to provide a continuous flow type of electronic particle studying apparatus for handling of heavier particles in which one of the vessels is electrically isolated from the fluid moving system.

A still further object of this invention is to provide means whereby all of the particulate matter of a sample may be recovered subsequent to its analysis by way of the Coulter type electronic particle analyzing apparatus.

A still further object of this invention is to improve the statistical sampling in a Coulter type electronic particle analyzing apparatus.

A still further object of this invention is to provide means for speeding the passage of particles through the vessels and aperture of the Coulter type electronic particle analyzing apparatus.

A still further object of this invention is to provide apparatus of the character described which will accept particles in the form of dry powders, and for plurries.

A still further object of this invention is to provide a Coulter type apparatus which conserves electrolyte by filtering and recycling it.

ABSTRACT OF THE INVENTION The invention is concerned with the counting and sizing of particles particularly those whose density and size make difficult dispersion in a liquid medium and to monitor, in its entirely, a particulate sample with recovery of the total sample subsequent to the testing.

The invention here provides apparatus wherein the original electrolyte is continuously fed with clean filtered electrolyte. The particulate matter to be measured is placed in the upstream chamber where it is immediately diluted. The extent of thedilution is immaterial since all of the particles are to be counted eventually. Since there is an electrolytic path existing between the upstream chamber and the clean electrolyte system, the said upstream chamber preferably is maintained at ground potential so that the downstream electrode, that is the electrode in the downstream chamber is other than ground, necessitating an electrical isolation of that chamber, this being provided by a drip chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the apparatus according to the invention in diagrammatic form.

FIG. 2 is a diagrammatic sectional schematic representation of the apparatus according to the invention.

FIG. 3 is an elevational section of the chamber portions of the apparatus diagrammatically illustrated in FIGS. 1 and 2.

FIG. 4 is a diagrammatic sectional schematic representation of a modified embodiment of the inventlon.

FIG. 5 is a plan view of the drip chamber portion of the apparatus according to the invention.

FIG. 6 is a diagrammatic sectional schematic representation of another modified embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, wherein the examining apparatus shall be designated generally by reference character 10 while the electrolyte supply system shall be generally designated by reference character 100. A successful arrangement of the apparatus and system may be provided by mounting the examining apparatus on the front side of a panel and the electrolyte supply system upon the opposite side of the panel with the conduit means therebetween passing through suitable openings in the panel, the panel itself not being shown in the illustrations.

Looking now at FIG. 2 and in particular to the examining apparatus 10, a pair of chambers 12 and 14 are defined by cylindrical vessels l6 and 18. Open top ves-' sel 16 is provided with a bottom flange 19 while vessel 18 is provided top and bottom flanges 21 and 23. A conical aperture holder 26 is disposed between the vessels 16 and 18 and has a tapered bottom opening 28 into which a collar 30 is sealingly engaged. The collar carries a central passageway having a narrow diameter portion which shall be referred to as an orifice 32. The upper wall surface 34 of the collar 30 is flattened and mounts fused thereon, a wafer 36 in which a microscopic dimension aperture 38 is formed. The wafer is mounted on the said surface 34 so that the aperture and orifice are coaxial. Reference may be made to US. Pat. No. 2,985,830 for details of the wafer, etc. Thus we have the Coulter scanning aperture means. The holder 26 for the Coulter scanning aperture means is provided with a flange 40 as the upper edge of the holder 26. Mounting or support blocks 42 and 44 are provided and preferably are formed of plastic electrical insulating material, such as for example, polypropylene. The pair of blocks 42 and 44 are joined together by means of screw type clamp means 46. (FIG. 3) Gaskets 48 and 50 make a sealed connection between the blocks 42 and 44 and vessel 18. A screwed on clamp 52 is secured to block 42 and an adjusting screw 54 is thereby engaged with the block 42 with the end 53 of the clamp arm 52' engaged on the flange 19 with gaskets 56 and 58 interposed between the flanges -19 and 21 and between flange 21 and block 42.

Passageways 60 and 62 are formed in blocks 42 and 44 respectively and lead to valve assemblies 64 and 66 respectively. Measuring electrodes 68 and 70 are introduced into the chambers 12 and 14 respectively,

with their lead wires passing through the walls of vessels 16 and 18 by way of a metalized glass electrodes 72 and 74 respectively. Block 44 has a plurality of axial passageways 76 and 78 formed therein and opening to a recess 8, the annular wall 82 thereof being tapered outwardly. The formation 84 in recess 80 is conical leading to a central apex 86. An annular groove 88 is formed in the surface 44' of block 44. The inner wall portion 88' of groove 88 is notched to receive an O-ring 90 therein. An open top vessel 2 of cylindrical configuration is received in the groove 88 and held therein by frictional contact with the 0-ring 90. The floor 94 of vessel 92 is tapered downwardly toward the axis leading to a conduit 96 and valve means 98. Conduits 96' and 96" lead to valve means 98' and 98".

Referring to the electrolyte supply and recirculation system 100, a storage tank 102 is provided with a filling top opening 104 capped by suitable cap 106. Conduit 108 opening from the tank 102 near the bottom thereof leads to a pump 110, the outlet portion 123 thereof then leading to a filter 114 and then, by conduit 116, to reservoir 118. The reservoir 118 is a closed vessel having the entry from conduit 116 opening at the bottom of said reservoir and having a line 120 leading from a location near the top of the reservoir back to the storage tank 102 to enter same via overflow opening 120. A source 122 of filtered air is coupled to the upper portion of reservoir 118. A line 124 leads from the source 122 to the storage tank 102 to enter at air inlet port 124'. The conduit 126 leads by way of valve means 128 to the upstream vessel 16 by way of line 130.

A trap 132 is provided connected to a regulated vacuum supply 134 by way of line 136. The downstream vessel 18 is coupled to the trap 132 by way of the conduit 138, passageway 60 and valve assembly 64. Valve means 98" is tapped into line 138 by way of line 140.

Valve means 98' is connected to cleaning probe 142 by way of flexible line 144, which may be formed of rubber or plastic tubbing. The probe is raised and lowered into and out from the vessel 16, as will be described hereinafter.

Suitable shielding indicated by broken line representation 146 is provided to surround all parts of the chamber 14 as to prevent spurious electrical paths effecting the measurement across the aperture 38.

Agitation means is provided in the form of a stirrer 146 driven by motor 148 and having an agitator tip 150 immersed within the first or upstream chamber 12. The electrodes 68 and 70 are connected to the detecting, counting and analyzing apparatus, indicated generally by box 152.

The operation of the invention may be most quickly understood by following the course of events as a given particulate sample as treated through the apparatus and utilizing system 100.

Electrolyte is supplied to the storage tank 102 by way of the opening inlet 104 until the level 154 reaches the air inlet 124 the overflow inlet 120". lnlet 104 is capped with cap 106. The pump 110 is activated, drawing electrolyte from the storage tank 102 by way of conduit 108 and forcing it through the filter 114 which retains all particles larger than a selected size, for example let us say those having a dimension exceeding 045 microns. The electrolyte then continues its travel by way of line 116 to the reservoir 118, the purpose of which is to reduce. the velocity of liquid flow past the opening to conduit 126. Electrolyte rises in the reservoir 118 until the surface 156 thereof rises higher than the outlet. 158 to the line 120, at which time further flow is returned by way of line and inlet 120' to the storage tank 102. The line 120 is joined to the reservoir 118 in a downwardly sloping manner, as shown at so that flow in the line 120 commences very quickly after the level 156 exceeds the lower edge of the outlet 158.

When the valve means 128 is opened, the electrolyte flows through conduit 126 and line into the upper chamber 12 defined by vessel 16. The electrolyte seeks its own level, thus causing the surface 160 to be at the same elevation as the surface 156 of reservoir 118.

Thus the upstream chamber 12 is filled with electrolyte and the lower chamber 14 remains to be filled. In order to fill lower chamber 14, valve means 64, 98 and 98' are placed in open condition and valve means 98" is closed. Cleaning probe 142 connected by way of line 144 is immersed in the electrolyte contained in the upper chamber 12. The regulated vacuum supply 134 is activated, evacuating the trap 132. Thus the vacuum is applied to the chamber 14 since valve means 98 and 98' are in open condition to the cleaning probe 142. Electrolyte is drawn through the cleaning probe 142 and line 144 and by way of valve means 98' and 98 is caused to rise into the chamber defined interior of vessel 92. The electrolyte will continue to rise until it encounters the passageways 76 and 78 through which it passes to enter the chamber 14. The electrolyte keeps rising and eventually enters the passageway 60. At this time the operator can place valve means 64 in closed condition. Thus we have now filled the chambers 12 and 14 as wellas the vessel 10 with electrolyte and, accordingly, provided them substantially free of air.

At this time, valve means 98' is placed in closed condition and the cleaning probe 142 is removed from the chamber 12. The valve 98" is now placed in open condition. Valve 66 is now open so that the interior of vessel 92 is connected by way of line 162 to the source of filtered air. With opening of valve 98" and 66, air enters the interior of vessel 92 forcing the electrolyte therefrom by way of valve means 98 and 98" and lines and 138 to the trap 132. When the operator notices the vessel 92 is substantially empty, valve means 66 is placed in closed condition. Now, with valve means 128 in the open position and valve means 98 and 98" in the open position, the electrolyte is constantly recirculated into the chamber 12. The only flow in the chambers is that permitted by passage through the aperture 38. The electrolyte which passes through this aperture 38 displaces electrolyte from the chamber 14 and causes dripage through passageways 76 and 78. The system is now ready for the addition of the particulate sample which will be studied.

A small sample of the particulate material to be studied, which is preferably in the form of dry powder so that it may be accurately weighed, is sprinkled on the surface of the electrolyte in chamber 12. The agitating means is in operation at the time of the addition so that the sample powder is directed into suspensides of vessel 16, until they can be passed through the aperture 38. With valve means 128, being in the open position, clean electrolyte is continuously being fed to the suspension. As the sample suspension is drawn through the aperture 38, the sample itself is diluted progressively and the particle count rate decreases. The decrease is one that is substantially exponential. When it decreases to a predetermined level selected by the operator on the basis of the accuracy desired, the count is terminated. It can be assumed that all the particles which were added have gone into suspension and have been counted.

The cleaningprobe 142 can be reintroduced into the vessel 16 and valve means 98" opened until air is drawn thereinto.

There are occasions where the electrolyte might be more valuable than the particles and in those occasions a positive displacement pump such as peristaltic pump 164 may be placed in the system 100 as shown in dotted outline in FIG. 2. This pump 164 must be capable of developing sufficient pressure to overcome that of the other pumps. If this is supplied the electrolyte is recycled and the particles are collected in the filter 114. It should be noted that conduits 98" and line 140 are arranged for gravity feed soas not to serve as particle traps. It also is important to note that the entry to passageway 62 from the vessel 92 is located to open at the highest possible location in the drip chamber defined by interior of vessel 92 so that all the air in the vessel 92 is removed when vessel 92 is filled with fluid electrolyte.

On occasion, it may be feasible to apply pressure to the upstream chamber 16. In FIG. 4, the examining apparatus 10' and supply system 100' differs from ap paratus l and system 100 in that the chamber 12 is closed off at the top to enable pressure to be applied, here for the purpose of speeding the flow of sample suspension through the sensing aperture 38. This is useful in order to provide shorter pulses to match the frequency response of the amplifiers used in the detecting, counting and analyzing apparatus 152. Also, the apparatus and system 100' uses more electrolyte so that with a reasonably short sample run, one can measure enough individual particles to give good statistical representation.

A lid 166 is placed on the vessel 16' and a reversable, positive displacement pump, such as peristaltic pump 168 is placed in the line 170 fed by the sample reservoir 172 by way of conduit 174. Line 170 also carries the electrolyte from reservoir 102, line 170 bottoming within the reservoir 102' at port 176. Reservoir 102' replaces the storage tank 102 and reservoir 118 of the system 100 and is vented at 178.

Since the reservoir 102' is vented, it is at atmospheric pressure and the pressure within the chamber 16 will be above atmospheric pressure by the pressure developed by pump 168. The fluid return system 96', 98', line 144 and cleaning probe 142 is eliminated.

The pressure within the drip chamber defined by vessel 92' is either at atmospheric pressure or is evacuated by a regulated vacuum supply 134 by way of lines 138 and 140 leading from trap 132, controlled by valve means 98" and 98 respectively. The pressure drop across the drip chamber is so small that practically all of the pressure appears across the aperture 38, hence accelerating the flow of electrolyte and sample therethrough. The flow of electrolyte from the reservoir 102' sucks sample from the sample reservoir 172 and the mixture of electrolyte and sample is complete by the time it gets to the chamber 16', where it undergoes further mixing due to the flow. The pressure developed by the pump 168 is measured by pressure gauge 180 in order to monitor the operation of the system In FIG. 6, another chamber 182 and another aperture 184 have been added to the apparatus 10' so that the apparatus 10" and system 100" can be utilized to monitor slurry in industrial usage which is usually tapped off a large line (not shown) and returned thereto. The peristaltic pump 186 is disposed in the sample line, here represented by line 188 having inlet 188' and outlet 188". The newly added chamber 182 and aperture 184 is interposed between the line 188 and the chamber 12", equilvalent to chambers 12 and 12 of earlier described apparatus 10 and 10'. The electrolyte fluid is introduced to the chamber 12" by way of line and peristaltic pump 168', and is connected back to its source (not shown) by way of line 170". Most of the electrolyte entering the chamber 182 leaves by way of outlet 188" but the slurry, passing in small amounts through the aperture 184, enters the chamber 12" and is mixed with the outflow at 170", thus diluting the particles of the slurry within the chamber 12". The outflow through 170" being regulated by differential pressure regulator means 173. The remaining portions of apparatus 10" are the same as that of apparatus 10 and 10'. Thus, the apparatus 10" and system 100" illustrated in FIG. 6 provides a continuously diluted slurry and the electronic observation of the particles going through the sensing aperture 38 can be performed at any convenient time. In the case of slurry study, the dilution could be carried out continuously.

While the examples of vessels 12, 14 and 92 have been described as providing flange type sealed connections one to the others, it is conceivable that such connections be replaced by using concentric telescoping cylinders in which the seals are provided by an O-ring, thickness of which is slightly greater than the difference between the inside radius of the larger vessel and the outer radius of the smaller vessel. Referring to FIG. 5, one will note that in addition to the passageways 76 and 78, the block 44 carries additional like passageways arranged in circular array about the axis of the recess 80. The passageways 76 and 78 only were described to diagrammatically illustrate the construction and operation of the apparatus and system according to the invention. The plural passageways aid to increase electrolyte fiow to the drip chamber defined by vessel 92.

I claim:

1. A system for the study of physical characteristics of particles not capable of retention in a fluid suspension compnsmg:

an electronic particle study apparatus including first and second vessels, scanning aperture means between said vessels to establish the sole communication path therebetween, each vessel having a fluid body electrically insulated one from the other except through the scanning aperture means, means establishing an electric current through the scanning aperture means and detecting means for detecting signals generated by the passage of particles through the scanning aperture means from one vessel to the other;

a fluid electrolyte supply system including a source of fluid electrolyte, for continuously supplying fluid electrolyte from the source of fluid electrolyte to one of the vessels,

a fluid recirculating system for conducting fluid electrolyte from the other of the vessels to the source of fluid electrolyte,

drip chamber means interposed between said other of the vessels and said fluid recirculating system electrically to isolate the vessels from said fluid supply and recirculating systems;

pump means for moving fluid electrolyte through said fluid supply and recirculating systems, and

collector means interposed within one of said fluid supply and recirculating systems for complete recovery of the total particles examined.

2. The system as claimed in claim 1 in which the first and second vessels comprise a pair of open-ended, superposed tubular members of insulating material and holder means interposed sealably between the tubular members, and said holder means including, a conical central portion having an opening in the center thereof and aperture carrying means sealingly engaged to said central portion within said opening and sealing means establishing a sealed juncture between both said vessels and said holder means.

3. The system as claimed in claim 1 in which the collector means comprises a filter.

4. The system as claimed in claim 1 and agitator means in said first vessel for dispersing particulate sample in the fluid body therein.

5. The system as claimed in claim 2 in which there is a third vessel of tubular configuration, block means for supporting said third vessel concentrically arranged relative to the second vessel, means establishing a sealed engagement of said block means with the second and third vessels, said block means having at least a pair of axial passages therethrough communicating between said second and third vessels, said block means having a recess formed therein and opening to said third vessel and conical abutment means formed within said recess, the apex of said abutment means arranged coaxial with said third vessel and with the passageways opening at the base thereof whereby fluid passing through said passageways travels along the abutment to the apex so that said drip chamber is defined by said block means and the interior of said third vessel, conduit means leading from said drip chamber to said fluid electrolyte recirculating system, and valve means interposed in said last mentioned conduit means.

6. The system as claimed in claim 2 in which there is a third vessel of tubular configuration, means for supporting said third vessel concentrically arranged relative to the second vessel and sealing means for establishing a sealed engagement between said first and second vessels and said holder means and valve means between said fluid supply and fluid recirculating systems and said second and third vessels.

7. The system as claimed in claim 2 in which there is a third vessel, means for sealably supporting said second and third vessels coaxially superposed one relative to the other and a separator sealably disposed between the second and third vessels, at least a pair of axial passageways formed in said separator to establish the only path for communication between the second and third vessels, said separator having a conical formation arranged concentric with said third vessel and said passageways opening to the base of said formation, the apex of said formation disposed within said third vessel coaxial therewith and conduit means at the base of said third vessel leading from the interior thereof to said fluid recirculating system, and valve means interposed within said last mentioned conduit means.

8. The system as claimed in claim 5 in which there is a vacuum trap interposed between said drip'chamber and said fluid recirculating system as a part thereof.

9. The system as claimed in claim 5 in which there is a cleaning probe means coupled between said third vesseland a movable member capable of being placed in communication with the interior of the first vessel and valve means disposed between said third vessel and said movable member.

10. The system as claimed in claim 8 and means sealably but releasably coupling the first, second and said third vessels one to the others.

11. The system as claimed in claim 10 wherein said last mentioned means comprises clamp means.

12. The system as claimed in claim 10 wherein said first vessel is covered and a positive displacement pump is disposed between the vessel and said fluid supply system.

13. The system as claimed in claim 10 wherein the first vessel is covered and a positive displacement pump is interposed between the first vessel and said fluid supply system and a sample aspirator is interposed between the source of fluid electrolyte and said pump.

14. The system as claimed in claim 13 in which said cover of the first vessel comprises a tap from an exterior sourceof particles and only a portion of said source particles enter the first vessel.

15. The system as claimed in claim 14 wherein said tap has a chamber communicating to said source by way of a pipe having inlet and outlet ports and a delivery port therebetween communicating to said chamber, and aperture means interposed between said chamber and the interior of the first vessel.

16. The system as claimed in claim 10 where the fluid supply system includes a source of filtered air under pressure and first and second conduit means arranged respectively between said source of filtered air and the second vessel, and said source of filtered air and said fluid supply system.

. 17. The system as claimed in claim 16 in which said fluid supply system includes ported storage means for storing fluid electrolyte, fluid inlet means leading from the second vessel to said storage means, air inlet means leading from said source of filtered air to said storage means and fluid outlet means leading from said storage means to said pump means and a fluid reservoir interposed between said pump means and the first vessel, and said collector means comprises a filter interposed between said first vessel and said fluid reservoir, the relative levels within said fluid reservoir and the first vessel arranged at the same level.

18. An electronic particle study apparatus for use in monitoring particles of nature incapable of being retained in fluid suspension and recovery of the said particles comprising;

means defining first and second chambers having first and second fluid bodies respectively therein, scanning aperture means disposed between said first 'and second chambers defining the only path of communication between said fluid bodies, electrical circuit means for establishing an electrical path through said aperture means whereby signals are generated by the passage of particles through said aperture means,

signal monitoring means capable of receiving said signals,

fresh fluid circulation means for introducing fresh filtered fluid to one of said chambers and including, a source of fresh fluid, first conduit means leading from said course to said one chamber, pump means interposed in said first conduit means between said source and said one chamber, filter means interposed in said first conduit means between said pump means and said one chamber and fluid flow control valve means in said conduit means,

fluid return means for returning fluid from said other chamber to said source and including second conduit means leading from said other chamber to said source, trap means interposed in said second conduit means and a regulated vacuum supply coupled to said trap means, and second fluid flow control valve means fluid flow in said second conduit means, and

a drip chamber interposed between the other of the chambers and the fluid return means electrically isolating said other chamber from said fluid return means.

19. The apparatus as claimed in claim 18 in which said drip chamber comprises an open top vessel sealably engaged with said second chamber and having a drain at the lower portion thereof, cover means disposed between the open top and the second chamber, said cover means including at least one axial passageway formed therethrough, a tapered formation extending into said vessel, the apex thereof being coaxial with said vessel and the passageway opening to the base of said formation whereby fluid leaving the second vessel by way of said passageway travels along said tapered formation to the apex for release into said vessel in the form of discrete drops.

20. The apparatus as claimed in claim 19 in which said drip chamber is placed between said second chamber andrsaid trip means and third fluid flow control valve means is interposed therebetween.

21. The apparatus as claimed in claim 18 and a source of filtered air, fourth conduit means between said source of filtered air and said drip chamber and fourth fluid flow control valve means associated with said fourth conduit means.

21 22. The apparatus as claimed in claim 18 and a fluid transfer system coupled between said drip chamber and cleaning probe means selectively introduced and withdrawn from said first chamber establishing flow therebetween during filling of said h ndd h e c i fi i ppaia tfs s i: aimed in claim 18 and secondary fluid conduit means leading between the source of fresh fluid and said trap means and a positive displacement pump disposed in said secondary fluid conduit means for leading fluid from the trap means to said fresh fluid source for circulation through said filter means.

24. In an electronic particle study apparatus of the type including first and second vessels, a scanning aperture means between said vessels to establish the sole communication path therebetween, each vessel having a fluid body electrically insulated one from the other except through the aperture means, means establishing an electric current through the aperture, means for detecting signals generated by passage of particles through the aperture from one vessel to the other, a suspension of particles in a fluid electrolyte medium being passed from a source of said suspension through said aperture means from the first vessel to the second vessel; the improvement comprising:

a fluid electrolyte supply system including a source of fluid electrolyte, for continuously supplying fluid electrolyte from the source thereof to one of the vessels,

a fluid electrolyte recirculating system for recirculating fluid electrolyte from the other of the vessels to the source of fluid electrolyte, a drip chamber interposed between said other of the vessels and said fluid recirculating system isolating the vessels electrically from said fluid supply and recirculating systems;

pump means operable to move fluid electrolyte through said fluid supply and recirculating systems, and

means interposed within one of said fluid supply and recirculating systems for complete recovery of the total particles examined. 

1. A system for the study of physical characteristics of particles not capable of retention in a fluid suspension comprising: an electronic particle study apparatus including first and second vessels, scanning aperture means between said vessels to establish the sole communication path therebetween, each vessel having a fluid body electrically insulated one from the other except through the scanning aperture means, means establishing an electric current through the scanning aperture means and detecTing means for detecting signals generated by the passage of particles through the scanning aperture means from one vessel to the other; a fluid electrolyte supply system including a source of fluid electrolyte, for continuously supplying fluid electrolyte from the source of fluid electrolyte to one of the vessels, a fluid recirculating system for conducting fluid electrolyte from the other of the vessels to the source of fluid electrolyte, drip chamber means interposed between said other of the vessels and said fluid recirculating system electrically to isolate the vessels from said fluid supply and recirculating systems; pump means for moving fluid electrolyte through said fluid supply and recirculating systems, and collector means interposed within one of said fluid supply and recirculating systems for complete recovery of the total particles examined.
 2. The system as claimed in claim 1 in which the first and second vessels comprise a pair of open-ended, superposed tubular members of insulating material and holder means interposed sealably between the tubular members, and said holder means including, a conical central portion having an opening in the center thereof and aperture carrying means sealingly engaged to said central portion within said opening and sealing means establishing a sealed juncture between both said vessels and said holder means.
 3. The system as claimed in claim 1 in which the collector means comprises a filter.
 4. The system as claimed in claim 1 and agitator means in said first vessel for dispersing particulate sample in the fluid body therein.
 5. The system as claimed in claim 2 in which there is a third vessel of tubular configuration, block means for supporting said third vessel concentrically arranged relative to the second vessel, means establishing a sealed engagement of said block means with the second and third vessels, said block means having at least a pair of axial passages therethrough communicating between said second and third vessels, said block means having a recess formed therein and opening to said third vessel and conical abutment means formed within said recess, the apex of said abutment means arranged coaxial with said third vessel and with the passageways opening at the base thereof whereby fluid passing through said passageways travels along the abutment to the apex so that said drip chamber is defined by said block means and the interior of said third vessel, conduit means leading from said drip chamber to said fluid electrolyte recirculating system, and valve means interposed in said last mentioned conduit means.
 6. The system as claimed in claim 2 in which there is a third vessel of tubular configuration, means for supporting said third vessel concentrically arranged relative to the second vessel and sealing means for establishing a sealed engagement between said first and second vessels and said holder means and valve means between said fluid supply and fluid recirculating systems and said second and third vessels.
 7. The system as claimed in claim 2 in which there is a third vessel, means for sealably supporting said second and third vessels coaxially superposed one relative to the other and a separator sealably disposed between the second and third vessels, at least a pair of axial passageways formed in said separator to establish the only path for communication between the second and third vessels, said separator having a conical formation arranged concentric with said third vessel and said passageways opening to the base of said formation, the apex of said formation disposed within said third vessel coaxial therewith and conduit means at the base of said third vessel leading from the interior thereof to said fluid recirculating system, and valve means interposed within said last mentioned conduit means.
 8. The system as claimed in claim 5 in which there is a vacuum trap interposed between said drip chamber and said fluid recirculating system as a part thereof.
 9. The system as claimed in claim 5 in which there is a cleaning probe means coupled between said third vessel and a movable member capable of being placed in communication with the interior of the first vessel and valve means disposed between said third vessel and said movable member.
 10. The system as claimed in claim 8 and means sealably but releasably coupling the first, second and said third vessels one to the others.
 11. The system as claimed in claim 10 wherein said last mentioned means comprises clamp means.
 12. The system as claimed in claim 10 wherein said first vessel is covered and a positive displacement pump is disposed between the vessel and said fluid supply system.
 13. The system as claimed in claim 10 wherein the first vessel is covered and a positive displacement pump is interposed between the first vessel and said fluid supply system and a sample aspirator is interposed between the source of fluid electrolyte and said pump.
 14. The system as claimed in claim 13 in which said cover of the first vessel comprises a tap from an exterior source of particles and only a portion of said source particles enter the first vessel.
 15. The system as claimed in claim 14 wherein said tap has a chamber communicating to said source by way of a pipe having inlet and outlet ports and a delivery port therebetween communicating to said chamber, and aperture means interposed between said chamber and the interior of the first vessel.
 16. The system as claimed in claim 10 where the fluid supply system includes a source of filtered air under pressure and first and second conduit means arranged respectively between said source of filtered air and the second vessel, and said source of filtered air and said fluid supply system.
 17. The system as claimed in claim 16 in which said fluid supply system includes ported storage means for storing fluid electrolyte, fluid inlet means leading from the second vessel to said storage means, air inlet means leading from said source of filtered air to said storage means and fluid outlet means leading from said storage means to said pump means and a fluid reservoir interposed between said pump means and the first vessel, and said collector means comprises a filter interposed between said first vessel and said fluid reservoir, the relative levels within said fluid reservoir and the first vessel arranged at the same level.
 18. An electronic particle study apparatus for use in monitoring particles of nature incapable of being retained in fluid suspension and recovery of the said particles comprising; means defining first and second chambers having first and second fluid bodies respectively therein, scanning aperture means disposed between said first and second chambers defining the only path of communication between said fluid bodies, electrical circuit means for establishing an electrical path through said aperture means whereby signals are generated by the passage of particles through said aperture means, signal monitoring means capable of receiving said signals, fresh fluid circulation means for introducing fresh filtered fluid to one of said chambers and including, a source of fresh fluid, first conduit means leading from said source to said one chamber, pump means interposed in said first conduit means between said source and said one chamber, filter means interposed in said first conduit means between said pump means and said one chamber and fluid flow control valve means in said conduit means, fluid return means for returning fluid from said other chamber to said source and including second conduit means leading from said other chamber to said source, trap means interposed in said second conduit means and a regulated vacuum supply coupled to said trap means, and second fluid flow control valve means fluid flow in said second conduit means, and a drip chamber interposed between the other of the chambers and the fluid return means electrically isolating said other chamber from said fluid return means.
 19. The apparatus as claimed in claim 18 in which said drip chamber comprises an open top vessel sealably engaged with said second chamber and having a drain at the lower portion thereof, cover means disposed between the open top and the second chamber, said cover means including at least one axial passageway formed therethrough, a tapered formation extending into said vessel, the apex thereof being coaxial with said vessel and the passageway opening to the base of said formation whereby fluid leaving the second vessel by way of said passageway travels along said tapered formation to the apex for release into said vessel in the form of discrete drops.
 20. The apparatus as claimed in claim 19 in which said drip chamber is placed between said second chamber and said trip means and third fluid flow control valve means is interposed therebetween.
 21. The apparatus as claimed in claim 18 and a source of filtered air, fourth conduit means between said source of filtered air and said drip chamber and fourth fluid flow control valve means associated with said fourth conduit means.
 22. The apparatus as claimed in claim 18 and a fluid transfer system coupled between said drip chamber and cleaning probe means selectively introduced and withdrawn from said first chamber establishing flow therebetween during filling of said chambers and drip chamber.
 23. The apparatus as claimed in claim 18 and secondary fluid conduit means leading between the source of fresh fluid and said trap means and a positive displacement pump disposed in said secondary fluid conduit means for leading fluid from the trap means to said fresh fluid source for circulation through said filter means.
 24. In an electronic particle study apparatus of the type including first and second vessels, a scanning aperture means between said vessels to establish the sole communication path therebetween, each vessel having a fluid body electrically insulated one from the other except through the aperture means, means establishing an electric current through the aperture, means for detecting signals generated by passage of particles through the aperture from one vessel to the other, a suspension of particles in a fluid electrolyte medium being passed from a source of said suspension through said aperture means from the first vessel to the second vessel; the improvement comprising: a fluid electrolyte supply system including a source of fluid electrolyte, for continuously supplying fluid electrolyte from the source thereof to one of the vessels, a fluid electrolyte recirculating system for recirculating fluid electrolyte from the other of the vessels to the source of fluid electrolyte, a drip chamber interposed between said other of the vessels and said fluid recirculating system isolating the vessels electrically from said fluid supply and recirculating systems; pump means operable to move fluid electrolyte through said fluid supply and recirculating systems, and means interposed within one of said fluid supply and recirculating systems for complete recovery of the total particles examined. 